Young people who give up smoking tobacco before reaching the age of 40 can reasonably expect to live nearly as long as others who’ve never smoking cigarettes at all, a new groundbreaking study of U.S. health and death records has shown.

Smoking, which can cut at least 10 years off someone’s lifespan, ensnares 30 million young adults each year (about half of all young men and 10% of young women) and most do not quit.

“Quitting smoking before age 40, and preferably well before 40, gives back almost all of the decade of lost life from continued smoking,” said Dr. Prabhat Jha, head of the Centre for Global Health Research at St. Michael’s Hospital in Toronto.

“That’s not to say, however, that it is safe to smoke until you are 40 and then stop,” said Jha. “Former smokers still have a greater risk of dying sooner than people who never smoked. But the risk is small compared to the huge risk for those who continue to smoke.”

Statistics Canada senior researcher Didier Garriguet says because of the type of study, one can only hypothesize as to why women’s health-related quality of life improves faster than men. But one reason may relate to the different smoking patterns of men and women.

“Women smoke less than men when they do smoke…. So that’s one possible explanation. Because we see that intensity also has a role to play in how long it takes to see the health benefits coming back to what they were when you were not a smoker at all,” Garriguet said in an interview.

Garriguet was not an author of either paper but was designated to answer questions on them. Two of the authors had retired and a third was on maternity leave.

The estimates of how long it takes for ex-smokers’ health status to approach that of those who have never smoked are averages.

‘For some smokers, they will never see their quality of life going back to the same thing’

The actual time would vary from person to person depending on factors like how long and how much they smoked.

“There will be differences between people, of course,” Garriguet said.

“Like for some people, it will probably take five years until they have the same quality of life. For some people, they will never see their quality of life going back to the same thing.”

On the specific issue of heart disease, however, one of the studies found that it takes ex-smokers — both men and women — about 20 years before their heart disease risk settles back to the level of non-smokers.

Daily smokers have a 60% higher risk of heart disease than people who never smoked

Current daily smokers have a 60% higher risk of heart disease than people who never smoked, one of the studies suggested.

“The major finding of this study is that long-term smoking cessation results in improvements in HRQL” — statistician-speak for health-related quality of life — “at any age,” said one of the studies. Both were released Wednesday in the Statistics Canada publication Health Reports.

The studies are based on data draw from the National Population Health Survey, which gathers information on the smoking status of Canadians every two years. For the studies, the authors looked at 16 years of data, or nine cycles of the survey covering the period from 1994-95 to 2010-11.

The percentage of Canadians aged 15 or older who smoked fell to 17% in 2010 from 35% in 1985

Over the period studied, the percentage of Canadians aged 15 or older who smoked fell to 17% in 2010 from 35% in 1985. Also over the period communities began to institute increasingly strict smoking bans, limiting the number of places smokers could indulge their habits.

For the study looking at how long it took for ex-smokers to become like non-smokers in terms of their health, the researchers looked at a sample of 3,341 men and 4,143 women aged 40 or older in 1994-95. They used people 40 and older because that is the time of life where the health problems of long-term smoking begin to become evident.

The other study, looking at the heart disease risk of smokers, looked at data from 4,712 men and 5,715 women aged 25 or older and free of heart disease in 1994-95.

During the 16-year period, 18% of the men and 14% of the women were either diagnosed with or died from heart disease. People who were daily smokers during the period were 60% more likely to have been diagnosed with, or to have died from, heart disease than the non-smokers in the group.

The risk rose with rate of consumption. Men who smoked 25 or more cigarettes a day were twice as likely to develop heart disease as men who never smoked. And even women who smoked fewer than 15 cigarettes a day had a 50% higher risk of heart disease when other factors related to heart disease were included in the model.

Quitting smoking helped to lower the heart disease risk of smokers, but over time. In fact, 20 continuous years of not smoking were needed before the ex-smokers’ risk of heart disease approached that of people who had never smoked daily.